930 resultados para The Wake


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Contiene Informe completo y resumen.

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The wake produced by the structural supports of the ultrasonic anemometers (UAs)causes distortions in the velocity field in the vicinity of the sonic path. These distortions are measured by the UA, inducing errors in the determination of the mean velocity, turbulence intensity, spectrum, etc.; basic parameters to determine the effect of wind on structures. Additionally, these distortions can lead to indefinition in the calibration function of the sensors (Cuerva et al., 2004). Several wind tunnel tests have been dedicated to obtaining experimental data, from which have been developed fit models to describe and to correct these distortions (Kaimal, 1978 and Wyngaard, 1985). This work explores the effect of a vortex wake generated by the supports of an UA, on the measurement of wind speed done by this instrument. To do this, the Von Karman¿s vortex street potential model is combined with the mathematical model of the measuring process carried out by UAs developed by Franchini et al. (2007). The obtained results are the correction functions of the measured wind velocity, which depends on the geometry of the sonic anemometer and aerodynamic conditions. These results have been validated with the ones obtained in a wind tunnel test done on a single path UA, especially developed for research. The supports of this UA have been modified in order to reproduce the conditions of the theoretical model. Good agreements between experimental and theoretical results have been found.

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Irregularities in observed population densities have traditionally been attributed to discretization of the underlying dynamics. We propose an alternative explanation by demonstrating the evolution of spatiotemporal chaos in reaction-diffusion models for predator-prey interactions. The chaos is generated naturally in the wake of invasive waves of predators. We discuss in detail the mechanism by which the chaos is generated. By considering a mathematical caricature of the predator-prey models, we go on to explain the dynamical origin of the irregular behavior and to justify our assertion that the behavior we present is a genuine example of spatiotemporal chaos.

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In the wake of the Arab Spring, the Southern Mediterranean region has reached a turning point in its history, presenting many opportunities and challenges for the EU. In this MEDPRO Policy Paper, Rym Ayadi and Carlo Sessa explore various possible scenarios that could play out in EU-Mediterranean relations over the next two decades but find, lamentably, that the EU has set itself on a ‘business as usual’ course, leaving the region open to further polarisation and the involvement of other external players.

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The outbreak of the Arab Spring and the unrest, revolution and war that followed during the course of 2011 have forced the EU to acknowledge the need to radically re-think its policy approach towards the Southern Mediterranean, including in the domain of migration. Migration and mobility now feature as key components of High Representative Catherine Ashton’s new framework for cooperation with the region (Partnership for Democracy and Shared Prosperity), while the EU has declared its intention to strengthen its external migration policy by setting up “mutually beneficial” partnerships with third countries – so-called ‘Dialogues for Migration, Mobility and Security’ – now placed at the centre of the EU’s renewed Global Approach to Migration and Mobility (GAMM). However, the success of this approach and its potential to establish genuine cooperative partnerships that will support smooth economic and political transformation in North Africa hinge on the working arrangements and institutional configurations shaping the renewed GAMM at EU level which has long been marked by internal fragmentation, a lack of transparency and a predominance of home affairs and security actors. This paper investigates the development of the Dialogues for Migration, Mobility and Security with the Southern Mediterranean in a post-Lisbon Treaty institutional setting. It asks to what extent has the application of the Lisbon Treaty and the creation of an “EU Foreign Minister” in High Representative Ashton, supported by a European External Action Service (EEAS), remedied or re-invigorated the ideological and institutional struggles around the implementation of the Global Approach? Who are the principal agents shaping and driving the Dialogues for Migration, Mobility and Security? Who goes abroad to speak on the behalf of the EU in these Dialogues and what impact does this have on the effectiveness, legitimacy and accountability of the Dialogues under the renewed GAMM as well as the wider prospects for the Southern Mediterranean?

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This study, commissioned by the European Parliament’s Policy Department for Citizen’s Rights and Constitutional Affairs at the request of the LIBE Committee, analyses the Schengen area in the wake of the European ‘refugee crisis’ and other recent developments. With several Member States reintroducing temporary internal border controls over recent months, the study assesses compliance with the Schengen governance framework in this context. Despite suggestions that the end of Schengen is nigh or arguments that there is a need to get ‘back to Schengen’, the research demonstrates that Schengen is alive and well and that border controls have, at least formally, complied with the legal framework. Nonetheless, better monitoring and democratic accountability are necessary.

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Mode of access: Internet.

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Imperfect copy: portion of t.p. containing imprint missing.

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"Westminster ed."

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Mode of access: Internet.